Critical and supercritical cleaning of hydrocarbon-containing materials

ABSTRACT

A method for cleaning materials containing solids and/or liquids is disclosed which involves contacting the materials with an extracting fluid including Xe, NH 3 , lower aromatics, nitrous oxide, water, CO, CO 2 , H 2 O, lower alcohols, lower alkanes, lower alkenes, or mixtures or combinations thereof under conditions of temperature and pressure sufficient to maintain the fluid at, near or above its critical point and to products derived therefrom.

RELATED APPLICATION

This application claims provisional priority to U.S. ProvisionalApplication Ser. No. 60/265,825 filed Feb. 1, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an efficient and cost effective methodfor treating hydrocarbon-containing materials to remove solids, water,sulfur and/or other contaminants.

More particularly, the present invention relates to a method forcleaning hydrocarbon-containing materials including oil-containingmaterials such as well-fluids, drilling fluids, used oils, oilcontaminated soils, or the like, under near critical, critical and/orsupercritical conditions to produce a clean solid residue, anhydrocarbon residue and an aqueous residue, where the hydrocarbonresidue is reusable, the solid residue is substantially free ofhydrocarbons and aqueously extractable contaminants and the aqueousresidue can be further cleaned to produce a purified water residue.

2. Description of the Related Art

Critical and supercritical extraction processes have been known for sometime. Supercritical extraction has been used to clean oil and todesulfurize coal, but the technique has not been used to clean updrilling fluids so that the cutting are substantially free ofhydrocarbon residue and/or aqueously soluble contaminants.

Thus, there is a need in the art for a method for cleaning drillingfluids and solid concentration derived therefrom generally viacentrifugation to a purified solid material substantially free ofhydrocarbon residues, drilling field chemicals and/or water solublecontaminants.

SUMMARY OF THE INVENTION

The present invention provides a solid residue substantially free oforganic and/or non-organic water-soluble components, where the solidresidue is derived from critical and/or supercritical extraction of amaterial including the solid, organic and/or non-organic water-solublecomponents with a cleaning composition comprising CO, CO₂, H₂O, loweralcohols, lower alkanes, lower alkenes or mixtures or combinationsthereof.

The present invention provides a water-insoluble liquid residuesubstantially free of solids and/or non-organic water-solublecomponents, where the liquid residue is derived from critical and/orsupercritical extraction of a material including the solid, organicand/or non-organic water-soluble components with a cleaning compositioncomprising CO, CO₂, H₂O, lower alcohols, lower alkanes, lower alkenes ormixtures or combinations thereof.

The present invention provides a hydrocarbon residue substantially freeof solids and/or water soluble components including organic andinorganic, water-soluble components or mixtures thereof, where thehydrocarbon liquid residue is derived from critical and/or supercriticalextraction of a material including the solid, organic and/or non-organicwater-soluble components with a cleaning composition comprising CO, CO₂,H₂O, lower alcohols, lower alkanes, lower alkenes or mixtures orcombinations thereof.

The present invention provides a method for cleaning a solid materialincluding contacting the mixture with a cleaning composition includingCO, CO₂, H₂O, lower alcohols, lower alkanes, lower alkenes or mixturesor combinations thereof under conditions of temperature and pressuresufficient to maintain the cleaning composition at, near or above itscritical point for a time sufficient to achieve a desired degree ofcleaning of the solid material.

The present invention provides a method for cleaning a mixture includingcontacting the mixture with a cleaning composition including CO, CO₂,H₂O, lower alcohols, lower alkanes, lower alkenes or mixtures orcombinations thereof under conditions of temperature and pressuresufficient to maintain the cleaning composition at, near or above itscritical point for a time sufficient to achieve a desired degree ofseparation of the mixture.

The present invention provides a method for cleaning a mixture includingcontacting the mixture including a solid component, a water-insolubleliquid component and water with a cleaning composition including CO,CO₂, H₂O, lower alcohols, lower alkanes, lower alkenes or mixtures orcombinations thereof under conditions of temperature and pressuresufficient to maintain the cleaning composition at, near or above itscritical point for a time sufficient to achieve a desired degree ofseparation of the mixture into a solid residue, a water-insoluble liquidresidue and an water-soluble liquid residue.

The present invention provides a method for cleaning a mixture includingcontacting the mixture including a solid component, a water-insolubleliquid component and water with a cleaning composition including CO,CO₂, H₂O, lower alcohols, lower alkanes, lower alkenes or mixtures orcombinations thereof under conditions of temperature and pressuresufficient to maintain the cleaning composition at, near or above itscritical point for a time sufficient to achieve a desired degree ofseparation of the mixture into a solid residue, a water-insoluble liquidresidue and/or an water-soluble liquid residue, where the solid residueis substantially free of organic and aqueously soluble components, thewater-insoluble liquid residue is substantially free of solids, water orwater-soluble components, and the water-soluble liquid residue issubstantially free of solids and water-insoluble liquid components.

The present invention provides a method for cleaning a mixturecontaining solids, organics such as hydrocarbons, inorganics such asmetal complexes, and/or water including contacting the mixture with acleaning composition including CO, CO₂, H₂O, lower alcohols, loweralkanes, lower alkenes or mixtures or combinations thereof underconditions of temperature and pressure sufficient to maintain thecomposition in a supercritial state for a time sufficient of achieve adesired degree of component separation.

The present invention provides a method for cleaning drilling fluids,oil contaminated soil, oil pit material, or the like includingcontacting a drilling fluid with a cleaning composition including CO,CO₂, H₂O, lower alcohols, lower alkanes, lower alkenes or mixtures orcombinations thereof under near critical, critical or supercriticalconditions.

The present invention provides a method for cleaning used motor oilsincluding contacting a used-motor oil with a cleaning compositionincluding CO, CO₂, H₂O, lower alcohols, lower alkanes, lower alkenes ormixtures or combinations thereof under near critical, critical orsupercritical conditions, to produce a reusable motor oil. Preferably,the reusable motor oil is substantially clear in color and has thecharacteristic of the motor oil prior to the addition of one or moreadditives, especially polar and/or water soluble additives. The reusablemotor oil also generally has a lower sulfur content that the sulfurcontent found in the used motor oil prior to cleaning.

The present invention provides a method for desulfurizing a hydrocarbonfuel such as fuel oil, gasoline, diesel fuel, jet fuel or similarhydrocarbon fuels including contacting a hydrocarbon fuel with acomposition including CO, CO₂, H₂O, lower alcohols, lower alkanes, loweralkenes or mixtures or combinations thereof under near critical,critical or supercritical conditions, to produce a hydrocarbon fuelhaving a sulfur content less than the sulfur content of the hydrocarbonfuel prior to cleaning.

DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdetailed description together with the appended illustrative drawings inwhich like elements are numbered the same:

FIG. 1 depicts a schematic diagram of a preferred embodiment of a batchtype apparatus for carrying out the process of this invention;

FIG. 2 depicts a phase diagram for carbon dioxide;

FIG. 3 depicts a graph depicting the pressure verses enthalpyrelationship for carbon dioxide;

FIG. 4 depicts a schematic diagram of a preferred embodiment of asemi-batch apparatus for carrying out the process of this invention;

FIG. 5 depicts a schematic diagram of one preferred embodiment of acontinuous apparatus for carrying out the process of this invention;

FIG. 6 depicts a schematic diagram of another preferred embodiment of acontinuous apparatus for carrying out the process of this invention;

FIGS. 7A&B depict a schematic diagram of two preferred embodiment of acontinuous apparatus for cleaning contaminated solid including drillingfluids, oil containing soils, or the like of this invention, where theextraction unit is shown in cross-section; and

FIGS. 8A&B depict a schematic diagram of two preferred embodiment of acontinuous multi-staged apparatus of this invention for cleaning and/ordesulfurizing used hydrocarbons including used motor oils or cleaningand/or desulfurizing hydrocarbon fuels including gasoline, fuel oil,diesel fuel, jet fuel or the like.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have found that an efficient and cost effective processfor cleaning solid materials and/or mixtures containing solid materialscan be developed using a cleaning composition at, near or above iscritical point. The processes of this invention can produce a solidresidue substantially free of hydrocarbons, water soluble contaminantsand/or other contaminants, a water-insoluble liquid residuesubstantially free of solids, water-soluble contaminants and/or othercontaminants and a aqueous residue substantially free of solids andwater-insoluble liquid contaminants.

The present invention broadly relates to a process for cleaning solids,dispersions, slurries, and/or liquids under near critical, critical orsupercritical fluid extraction where the extracting fluid includes Xe,NH₃, lower aromatic including benzene and toluene, nitrous oxide, water,CO, CO₂, H₂O, lower alcohols including methanol, ethanol, propanol, andisopropanol, lower alkanes including methane, ethane, propane, butane,pentane and hexane, petroleum ether, lower alkenes including ethyleneand propylene or mixtures or combinations thereof.

The process is ideally suited for cleaning drilling fluids, reactorsludge, oil-contaminated soils, oil contaminated water, used oil,hydrocarbon fuels such as diesel fuel, jet fuel and other similarhydrocarbon fuels, extracting oils from tar sands or the like, tankerbottoms, refinery bottoms, pit residues, refinery waste streams,refinery residue streams or the like. The pit residue include anymaterial that comprises oil and solid materials such as soil, dirt orthe like. The pit residue is generally associated with refining and/orseparation and/or processing of crude oil streams. The present inventioncan also be used to extract hydrocarbon material out of paint wastes,polymer waste or any other chemical processing waste or waste streamthat contains hydrocarbon materials, solid materials, water and/or othercomponents that are amenable to near critical, critical and/orsupercritical extraction.

The process results in purified hydrocarbons, purified solids, and/orpurified water. However, near critical, critical and/or supercriticalextraction is generally combined with other downstream waterpurification process to produce a purified water.

Drilling fluids are complex compositions that are the by-product of oilwell drilling operations. These fluids can include solids from drillingoperations, muds or other additives or compounds used in drillingoperations, greases, anti-seize compounds, hydrocarbons from hydrocarbonbearing formations, water, heavy metals, fracturing compositions,proppants, or other ingredients and mixtures and combination thereof.Drilling fluids can be in the form of a mixture of liquids and solids, adispersions, a suspension, an emulsion, or any other liquid like mixtureof solids and liquids.

Drilling fluid solids are solids obtained from an initial separation ofsolids from liquid components of a drilling fluid mixture. The solidsare generally obtained via centrifugation of the drilling fluids as iswell-known in the art. The solids generally have the appearance of a tarlike material, but can be any solid like material derived from a processwhich removes most liquid material from the drilling fluids.

The process is also ideally suited for cleaning hydrocarbon-containingfuels such as diesel fuel, jet fuel, home heating oil and other similarhydrocarbon fuels, or even gasoline. The process results in purifiedhydrocarbon-containing fuels having reduced sulfur contents and a sulfurcontaining residue. The fuel to be treated is contacted with a treatingsolvent or composition under near critical, critical and/orsupercritical conditions of temperature and pressure. The treatmenttemperature is usually from about 100° to about 400° C.

The process is also ideally suited for cleaning used motor oils toproduce a reusable motor oil. Because the cleaning process removesmaterial that are polar, many to all of the polar additives may beremoved during the extraction system. Therefore, in one preferredreusable oil product of this invention, additives or additive packagesare added into the cleaned oil. These additives can include any additivecurrently added to motor oils to improve their detergent properties orother properties.

Suitable extracting fluid include, without limitation, Xe, NH₃, loweraromatic such as benzene, toluene, or xylene, nitrous oxide, water, CO,CO₂, H₂O, lower alcohols such as methanol, ethanol, propanol, orisopropanol, lower alkanes such as methane, ethane, propane, butane,pentane hexane, or petroleum ether; lower alkenes such as ethylene orpropylene; or mixtures or combinations thereof. Preferably, theextracting fluid includes carbon dioxide, water, lower alkanes, loweralcohols, or mixture or combinations thereof. Particularly, theextracting fluid comprises a major portion of CO₂ and a minor portion ofa secondary fluid selected from the groups consisting of Xe, NH₃, loweraromatics, nitrous oxide, water, CO, H₂O, lower alcohols, lower alkanes,lower alkenes and mixtures or combinations thereof, where a majorportion means greater than 50 mol % carbon dioxide, preferably, greaterthan 70 mol % carbon dioxide, particularly, greater than 90 mol % carbondioxide, and especially, greater than 95 mol % carbon dioxide . Moreparticularly, the extracting fluid is exclusively carbon dioxide.

Tabulated below are critical conditions for various supercriticalfluids:

Critical Critical Critical temperature pressure Volume Fluid Tc (° K.)Pc (MPa) Vc (cm³/mol) Carbon dioxide 304.14 7.375 94 Water 647.14 22.0656 Ethane 305.32 4.872 145.5 Ethene 282.34 5.041 131 Propane 369.834.248 200 Xenon 289.73 5.84 118 Ammonia 405.5 11.35 75 Nitrous oxide309.57 7.255 97 Fluoroform 299.3 4.858 133 Methanol 190.56 4.599 98.60Isopropanol 508.3 4.764 222 Toluene 591.75 4.108 316

For the purposes of this invention, the term substantially free meansthat the cleaned component includes less than or equal to about 5 wt %of any given contaminant, preferably, less than or equal to about 2.5 wt% of any given contaminant, particularly less than or equal to about 2wt % of any given contaminant and especially less than or equal 1 wt %of any contaminant.

The material-to-be-treated is contacted with treating solvent undersupercritical conditions of temperature and pressure. The term,“supercritical,” “supercritical state,” “supercritical conditions,” or“supercritical conditions of temperature and pressure,” refers to atemperature above the critical temperature (Tc) of the solvent beingused, and a pressure above the critical pressure (Pc) of the solventbeing used. The treatment temperature is usually from 470° to 630° K.All temperatures herein will be given in degrees Kelvin (° K.) or degreeCelsius (° C.) unless otherwise stated. Treatment according to thisinvention is carried out at a reduced temperature (Tr) from 1.0 to about1.4, preferably from about 1.05 to about 1.3, and at a reduced pressure(pr) from 1.0 to about 2.0, preferably from about 1.05 to about 1.5. Theterm, “critical,” “critical state,” “critical conditions” or “criticalconditions of temperature and pressure,” refers to a solvent at itscritical temperature, Tc, and its critical pressure, Pc. The term, “nearcritical,” “near critical state,” “near critical conditions” or “nearcritical conditions of temperature and pressure,” refers to a solvent atmost about 10° C. below its critical temperature, Tc, and at most about10 psi below its critical pressure, Pc, and preferably, at most about 5°C. below its critical temperature, Tc, and at most about 5 psi below itscritical pressure, Pc.

The solvent to material-to-be-treated ratio for treatment according tothis invention can range from about 0.2 to about 3 kilograms of solventper kilogram of material-to-be-treated (Kg/Kg) preferably from about 0.3to about 1.0 Kg/Kg. Actually, the solvent to material-to-be-treatedratio is a dimensionless number, since both the amount of solvent andthe amount of material-to-be-treated are expressed on a weight basis.

The present invention can make possible the use of a much lower solventto material-to-be-treated ratio than those used in prior art processesat the lower end of the solvent to material-to-be-treated range.However, the process of the present invention can be operated at anyratio to achieve a desired result.

The solvent flow rate is generally from about 0.2 to 3 kilograms perhour of solvent per kilogram of material-to-be-treated per hour (i. e.,0.2 to 3 kg/kg-hr). Preferably the solvent flow rate is about 0.5kg/kg-hr. The time of treatment may range from about 0.5 to about twohours, and is preferably about one hour.

The material-to-be-treated may be treated in either a single stage or inplurality of stages (i.e., in two or more stages). In single stageextractions or treatments, the composition of the treating solventremains uniform over the entire course of treatment, and can be anysolvent described above, but is preferably carbon dioxide alone or incombination with water, a lower alcohol or a lower hydrocarbon. Inplural stage extractions or treatments, the composition of the treatingsolvent can be the same or different from stage to stage. For some usingmulti-staged treatment applications, the critical temperature of thetreating solvent used in each stage increases progressively. Thus, thefirst stage solvent may be a carbon dioxide; next a mixture of carbondioxide and water, or carbon dioxide and methanol; the solvent for thenext stage may be, for example, a mixture of methanol and water with nocarbon dioxide and so on. In extreme cases, the material-to-be-treatedmay be contacted consecutively with each of the treating fluids, i. e.,first with carbon dioxide, then with methanol, and finally with water,each in pure or substantially pure form. Whenever the composition of thesolvent is varied over the course of treatment, the overall solventcomposition (based on the total quantities of each treating fluid usedover the entire course of treatment) is as stated above, i.e., the molefraction of carbon dioxide is from 0 to 0.5 (preferably 0.05 to 0.25),the mole fraction of methanol is from 0.20 to 0.70 (preferably 0.30 to0.50), and the mole fraction of water is from 0.20 to 0.70 (preferably0.25 to 0.65).

In many of the preferred processes of this invention, carbon dioxidealone is the preferred extraction fluid. Thus, in multistageapplication, only the amount of carbon dioxide being supplied to eachstage may vary. Again, the carbon dioxide supplied in the first stageprogresses with the material-to-be-treated to the next stage. Thus asadditional carbon dioxide is supplied, the ratio to carbon dioxide tothe material-to-be-treated changes. Additionally, each stage can beoperated at a different temperature and/or pressure to achieve a desiredfinal product.

For solid type materials, a fixed bed, a moving bed reactor or othersimilar reactors can be used. Such reactor systems are described in moredetail hereinafter. When the material-to-be-treated is a fluid (slurry,liquid, dispersion, suspension, mixture, or the like) at treatmenttemperature, a conventional stirred reactor or other type of batch,semi-batch or continuous reaction system can be used. For materials thatinclude a large amount of solids such as drilling fluids, a preferredcontinuous system includes a tube within a tube within a tube typereactor described in more detail in disclosure associated with FIG. 8.For materials, such as used motor oil, which generally, do not include alarge amount of solids, a preferred system includes a series ofextraction units described in more detail in the disclosure associatedwith FIG. 9. This same type of multi-staged systems is ideally suitedfor reducing the sulfur content of hydrocarbon based fuels.

This invention will be further described and illustrated with referenceto the drawings which represent preferred embodiments of systems forcarrying out the processes of this invention, i.e., processes designedto convert drilling fluids are solids therefrom into a cleaned solidresidue, a non-aqueous residue and an aqueous residue.

System and System Operation

Referring now to FIG. 1, a preferred embodiment of an extraction systemgenerally 100 for use in the present invention is shown to include asource of a supercritical solvent 102, in this case carbon dioxide. Thesource 102 is connected to a sight glass 104 and a filter 106 via tubing108. The tubing 108 is also connected to a rupture disk relief valve 110for safety purposes. The filter 104 is connected to a pump 112 having aback pressure regulator 114 via tubing 108. The pump 112 is connected toa top entry 116 of an extraction cell 118 via tubing 108 including apressure gauge 120, a supply control valve 122 and a second rupture diskrelief valve 124. The cell 118 includes a bottom entry 126 and a sensor128. The top entry 116 is also connected to a top outlet valve 130 viatubing 108; the bottom entry 124 is connected to a bottom outlet valve132 and a bleed control valve 134, which is intern connected to a bleedvalve 136. The top and bottom outlet control valves 130 and 132 areconnected to a separation vessel 138 via a separator control 140 and aheat exchanger 142 including a second pressure gauge 144 and a bleedvalve 146. The separator 138 includes a sensor 148, a carbon dioxideoutlet 150 and a cleaned material outlet 152 having a control valve 154which can be connected to a cleaned material container (not shown). Thecarbon dioxide outlet 150 connects to a used carbon dioxide venting line156 includes a back pressure regulator 158, two filter 160, an flowregulator 162 and an exhaust line 164, which can be a recycle line byconnecting the line to the pump 112. The entire system is amenable tocomputer control using standard computer control systems as are all ofthe other systems described herein.

The system of 100 operates by charging the cell 118 with amaterial-to-be-treated. Once the cell 118 is charged, valves 130, 132,134, and 136 are closed and valve 122 is opened to allow carbon dioxideto be pumped into the charged cell 118 via the pump 112 until asupercritical state is reached as indicated by the sensor 128. After theextraction has been allowed to run for a specified period of time, thevalve 122 is closed and the pump 112 is generally turned off. Aftervalve 112 is closed, the valves 130 and 132 are opened allowing thecontents of the cell 118 to flow through valve 140, which reduces thepressure of the transferred contents, and the heat exchanger 140 to warmthe contents up after pressure reduction and into the separator 138, viaan inlet 139. In the seperator 138, the now gaseous carbon dioxide istaken out of separator 138 through outlet 150 via venting line 156 andassociated equipment to either be exhausted to the air or recycled. Thecleaned material exits the separator 138 through outlet 152 controlledby the control valve 154.

The system shown in FIG. 1 is a preferred embodiment of an extractionsystems, but is simply an illustrative example of a system for treatingmixtures containing solids, hydrocarbons and water. Both the piping andfittings together with instrumentation can be configured in manydifferent ways to obtain the same result.

In a batch type operation, a sample is placed into a cell. The cell isthen sealed and the solvent is pumped into the cell under conditions oftemperature and pressure sufficient to maintain the solvent at, near orabove its critical point—near critical, critical and supercriticalconditions. In a continuous operation, the solvent and the material tobe separated would be continuously supplied to an extraction cell andsolid-containing and liquid-containing residues would be continuallyremoved from the cell. In either case, after contacting the solvent withthe sample, the liquid phase is allowed to separate into an organicphase and an aqueous phase which can then be separated by conventionalmeans such as decantation, stripping, distillation, or the like. Thesolids are either removed when the cell is opened or collectedcontinuously for post extraction treatment.

In the examples that follow a batch extraction system as shown in FIG. 1was used. The cuttings samples were placed into the chamber and thechamber or cell was then sealed. Carbon Dioxide from a standardcommercial cylinder was fed into the suction side of the pump. The pumpwas then switched on and the pressure of CO₂ was increased until itreached the critical point. The critical point of CO₂ is a function oftemperature and pressure as is the critical point for any other solventsystem. For CO₂ this dependence is shown in FIG. 2. FIG. 2 two is astandard phase diagram generally 200 for CO₂ is shown to include a vaporregion 202, a liquid region 204, a solid region 206 and the criticalpoint 208. Referring now to FIG. 3, a CO₂ pressure—enthalpy diagramgenerally is shown. The super critical fluid, CO₂, is fed into theextractor vessel whereupon the super critical fluid diffuses through thesolids and removes the oil or hydrocarbons or other supercritical CO₂soluble components, which contaminates the solid, into solution. Thecontaminants may be minerals, hydrocarbon (natural or synthetic). In thecase of drilling fluid, the contaminants will also include additives tostabilize the drilling well fluids, including, without limitation,Polyalphaolefins, Acetals, Isomerised Olefins, Linear Alpha Olefins,Linear Alkylbenzenes, drilling muds or mixtures or combinations thereofor the like.

From the reactor vessel the solute loaded super critical fluid passesthrough a heated metering valve where it is depressurized and separationoccurs, depositing the extracted oil and additives into the separationvessel. The super critical fluid (now in the gas phase) is exhausted tovent through a flow meter and totalizer. In a commercial full scaleoperation, the Carbon Dioxide gas or other fluid composition would becollected and fed back to the suction (low pressure) side of the pump,thereby creating a closed loop system. Samples of the extracted mediumcan be taken from the liquid phase to determine a desired degree ofhydrocarbon removal. The chamber may require heating in certaincircumstances.

The solid which was not taken into solution by the supercritical phase,remains in the reaction vessel for subsequent removal. Aftersupercritical extration, the solid residue not only has reducedcontaminants, preferably substantially no supercritically solublecontaminant, but is dry and a sterile.

Referring now to FIG. 4, another preferred systems generally 400 forperforming the extraction method of this invention is show where theextracting solvent is a mixture of carbon dioxide, pure water, and puremethanol. The pure water and pure methanol are contained in liquid formin feed reservoirs 402 and 404, respectively, having exit flow controlvalves 406 and 408, respectively. Liquid water and liquid methanol areintroduced from reservoirs 402 and 404, respectively, into a liquid feedline 410. The water/methanol mixture is pumped through feed line 410 bymeans of a high pressure duplex reciprocating piston pump 412. Thiswater/methanol mixture flows to a mixing tee 414.

Carbon dioxide is stored as a liquid under pressure in a pressure vessel416, which may be a conventional gas cylinder. Carbon dioxide iswithdrawn as a gas or vapor from the container 416 into a gas line 418.Carbon dioxide flow from the container 416 is controlled by a pressureregulator 420. The feed rate of carbon dioxide through the line 418 tothe extractor 422 is controlled by a mass flow controller 424 and acontrol valve 426. Carbon dioxide is then passed through a pulsesuppressor 428 and a feed pre-heater 430 to insure smooth flow of thecarbon dioxide stream to a gas compressor 432. Carbon dioxide is thencompressed in the gas compressor 432 and the flow of compressed carbondioxide is stabilized by passing it through a flow stabilizer 434. Thecarbon dioxide stream flows from the stabilizer 434 to the mixing tee414.

The carbon dioxide stream is then mixed with the methanol/water mixturein the mixing tee 414. The combined mixture is then pre-heated in a feedpre-heater 436 to a temperature close to but slightly below the desiredreaction temperature. The heated solvent mixture is then fed via asolvent feed line 438 to the extractor 422, which has a fixed orstationary bed 440 therein. The fixed bed 440 is designed to contain anamount of a composition to be subjected to supercritical extraction,where the composition is either drilling solids from a centrifuge ordrilling fluids directly for a well site.

The extractor 422 is of a generally vertical tubular shape—a verticallydisposed tubular reactor, which is surrounded by a heating jacket 442having an electric heater 444 positioned therein. A foraminous plate 446at a bottom 448 of the extractor or reactor 422 supports the bed 440.The extractor 422 is provided with a rupture disc 450 and a pressuregauge 452. The extractor 422 is also provided with a temperature sensoror indicator 454, which indicates the temperature in the bed 440, and atemperature controller 456, which controls the current to the electricheater 444 in response to a reaction temperature as sensed bytemperature indicator 454.

During extraction, the extractor is held under conditions of temperatureand pressure sufficient to maintain the solvent at, near, but below orabove the solvents critical point—maintained under near critical,critical or supercritical conditions—as it passes downwardly through thebed 440. The effluent exits the reactor 422 at an outlet 458 and theeffluent will include the solvent and some or all components soluble inthe solvent (depending on the degree of intended cleaning or treatment)from the material-to-be-treated in the bed 440 such as organics,inorganics or the other compounds soluble in the extraction solventunder near critical, critical or supercritical conditions. The rate ofremoval of the exiting solvent is controlled by a control valve 460,which may be a needle valve. The normally liquid components of theeffluent, i.e., water, methanol, and liquids extracted by the solventare condensed by passage through a tubular condenser 462. The condenser462 is cooled by any suitable means such as a dry ice-acetone bath 464.The condensed liquids may be removed periodically (e.g., at the end of arun) from the condenser 462 for analysis. Uncondensed gases, typicallycarbon dioxide and normally gaseous hydrocarbons, are vented from thecondenser 462 through a vent line 466. These gases may be analyzed asdesired and the carbon dioxide recovered for recycling. Additionally,the volatile hydrocarbons can be collected for further processing. Thecalorific value of the vent gases in the line 464 may be recovered,e.g., by combustion of the gas mixture, where the calorific value issufficient to justify this. Of course, if the above reaction system isrun using only one solvent component, then the other solvent componentfeed lines are simply turned off or by-passed.

According to a preferred embodiment of a process of this invention,centrifuged drilling solids and/or fluids are charged to the reactor 422prior to the start of a run. Water, methanol and carbon dioxide are fedto the reactor 422 in desired proportions, which can run from purecarbon dioxide, pure methanol, pure water or any mixture or combinationthereof. The respective feed rates are controlled by means of the valves406 and 408 and the mass flow controller 424. The solvent feed mixtureis pre-heated in pre-heater 436 to a temperature just below the criticaltemperature of the solvent composition. The solvent mixture is passeddownwardly through the bed 440 in the reactor 422, where it is operatedunder conditions of temperature and pressure sufficient to maintain thesolvent near its critical point, at ites critical point or above itscritical point—near critical condition, critical conditions orsupercritical conditions—by means of external heat supplied by theelectric heater 444. The effluent exiting the reactor 422 includes thesolvent and all solvent soluble components with the solid being left inthe bed 440 is continuously removed and is condensed as previouslydescribed. A run is allowed to proceed either for a predetermined lengthof time or for a length of time determined by some other parameter, suchas instantaneous effluent analysis. Normally the solvent composition,i.e., the relative proportions of water, methanol and carbon dioxide,will remain constant throughout a run. This mode of operation may bedescribed as semi-batch, since the solids and/or fluids are charged toand the solids are discharged from the extractor 422 before and after arun, respectively, in accordance with batch operation principles, whilethe solvent mixture is fed continuously throughout a run. Of course, thereaction can be run with non-continuous solvent feed, which would beunder purely batch operating principles.

Semi-batch operation as described in FIG. 4 may be carried out in two ormore stages, using solvents of different compositions in each stage. Thesolvent used in each stage may be Xe, NH₃, lower aromatic includingbenzene and toluene, nitrous oxide, water, CO, CO₂, H₂O, lower alcoholsincluding methanol, ethanol, propanol, and isopropanol, lower alkanesincluding methane, ethane, propane, butane, pentane and hexane,petroleum ether, lower alkenes including ethylene and propylene ormixtures or combinations thereof. Using valves and flow controllers, anoperator can pass a solvent of any desired composition into anappropriate extractor. When more than one stage is used, the first stage(the earliest portion of the run) typically uses the most volatilesolvent (i.e., the solvent having the lowest critical temperature), andthe solvent or solvent mixtures used in subsequent operating stagestypically have progressively higher critical temperatures. However, eachstage can use the same solvent composition.

The present invention can also be operated under continuous operatingconditions using reactors systems such as those illustrates in FIGS. 5and 6. Referring now to FIG. 5, a preferred continuous system generally500 for performing the extraction method of this invention is shown toinclude a stirred high-pressure vessel 502, which serves to mix thematerial-to-be-treated such as drilling fluids or a solids with thesolvent. The material-to-be-treated and the supercritical extractionsolvent are fed to the vessel 502 via a feed line 504 and a solvent feedline 506, respectively. The solvent entering through the line 506 is asolvent selected from the group consisting of Xe, NH₃, lower aromaticincluding benzene and toluene, nitrous oxide, water, CO, CO₂, H₂O, loweralcohols including methanol, ethanol, propanol, and isopropanol, loweralkanes including methane, ethane, propane, butane, pentane and hexane,petroleum ether, lower alkenes including ethylene and propylene ormixtures or combinations thereof. The resulting slurry, dispersion romixture is then pumped by a high-pressure slurry pump 508 through a feedpreheater 510, which serves to heat up the mixture to a temperature justbelow the extraction temperature. The preheated feed is then admittedthrough a ball valve 512 or other similar device into a supercriticalextractor 514 which is of the stirred reactor design, a mixing extruder,or other similar high shear mixing reactors. The mixture containing theextracted non-solid components is passed through a discharge valve 516into a product cooler 518. The cooled product is next sent to aseparating vessel 520 in which the gaseous product of extraction areseparated from the cleaned solids and the liquid products. The gaseousproduct are either vented from the system 500 through valve 522 orseparated to recover carbon dioxide or to a system to recoverhydrocarbons or to recover fuel equivalents thereof. The solid andliquid products are removed through a valved discharge line 524.

Referring now to FIG. 6, another configuration for a continuoussupercritical extraction system generally 600 for performing theextraction method of this invention is shown to include a storage hopper602 containing a solid material-to-be-treated such as drilling solids,where a level of solids in the hopper 602 is controlled via a solidlevel indicator-controller 604. The solids are metered from the storagehopper 602 through a rotary air lock feeder 606 or via a screw typeextruder or other similar apparatus into an extractor 608. A solventmixture is fed into the extractor 608 through a solvent feed line 610.This solvent is selected from the group consisting of Xe, NH₃, loweraromatic including benzene and toluene, nitrous oxide, water, CO, CO₂,H₂O, lower alcohols including methanol, ethanol, propanol, andisopropanol, lower alkanes including methane, ethane, propane, butane,pentane and hexane, petroleum ether, lower alkenes including ethyleneand propylene or mixtures or combinations thereof, which may be formed,pressurized and preheated to just below the critical temperature asdescribed with reference to FIG. 5. The solvent can be analyzed forcompositional makeup using a gas chromatograph 612. The system shown inFIG. 6 differs from that shown in FIG. 5 in that the system of FIG. 5can be operated only co-currently, while the system of FIG. 6 can beoperated either under counter-current or co-current flow conditions. Amixture of extracted and cleaned solids discharged from the extractor608 is cooled in a product cooler 614 before being let down through avalve 616 into a product separating vessel 618. In this vessel, thegaseous products of extraction are separated from the cleaned solids andthe liquid products. The gaseous product is then vented from the systemthrough a valve 620. The cleaned solids and liquid products aredischarged through a valve 622 and separated as described above.

Referring now to FIGS. 7A&B, a preferred configuration for a continuoussupercritical extraction system, generally 700, for performing theextraction method of this invention for solid and/or slurry materials isshown to include an input container 702 containing a solidmaterial-to-be-extracted 703 such as drilling fluids.

The solids are metered from the container 702 through a control/meteringsystem 704 into an extractor 706 via lines 707, where thecontrol/metering system 704 can be a pump, a rotary air lock feeder, ascrew type extruder, a value, or other control/metering apparatus. Itthe container 702 is pressurized, the controller 704 can be a remotecontrolled valve, but generally, the controller 704 is a pump.

The extractor 706 comprises a tube within a tube within a tube typeextractor. The extractor 706 includes an outer column or tube 708 a, asemi-permeable membrane 710, a lower section 712 a and an upper section712 b. The upper section 712 b includes a closed ended, inverted middletube 708 b and an inner tube 708 c. The extractor 706 also includes amaterial-to-be-extracted inlet 714 connected to one of the lines 707from the controller 704A. The inlet 714 passes through the membrane 710delivering the material-to-be-extracted 703 into an interior 716 of theinner tube 708 c from the container 702. The dashed lines with arrowsindicate the direction of material flow in the extractor 706. The innertube 708 c extends upward to form a first gap 718 a between a top 720 ofthe inner tube 708 c and an inner surface 722 of the closed end 724 ofthe middle tube 708 b. The middle tube 708 b extends downward to form asecond gap 718 b between a top 711 of the membrane 710 and a bottom 726of the middle tube 708 b. While a third gap 718 c is formed between anouter surface 728 of the closed end 724 of the middle tube 708 b and aninner surface 730 of a top 732 of the column 708 a. The inner surface730 is shown here to include a tapered section 731 to improve materialflow out of the extractor 706. The gaps 718 a, 718 b and 718 c may havethe same dimension or may have different dimensions and are designed toprovide shear mixing of the material-to-be-extracted and the extractingfluid as the combined flow progressed through the extractor 706 alongthe path indicated by the dashed and arrowed lines.

The extractor 706 also includes extraction fluid inlets 734 a, 734 b and734 c adapted to supply an extraction fluid 736 from an extraction fluidsupply system 738 to the extractor 706 via lines 735 a–c. The inlet 734c supplies a first amount of extraction fluid 736 into the inner tube708 c at a position 740 near a top 715 of the inlet 714 via line 735 c.The inlet 734 b supplies a second amount of extraction fluid 736 vialine 735 b into the middle tube 708 b at a position 742. The position742 can be at any desired location along the middle tube 708 b, but ispreferably located near the gap 718 b. The inlet 734 a supplies a thirdamount of extraction fluid 736 via line 735 a into the outer tube 708 aat a position 744. Although the position 744 can be located anywherealong the column 708 a, it is preferably located near the gap 718 b.

The supply system 738 includes an extraction fluid storage tank 746, acompressor 748, and a mass controller 750. The compressor 748 compressesthe extraction fluid 736 to a desired pressure, which is preferably apressure that is sufficient to maintain the extraction fluid in theextractor to be at or above the supercritical point for the particularextraction fluid being used. Looking at FIG. 7A, the system 738 alsoincludes separate valves 752 a–c for controlling the first, second, andthird amount of extracting fluid flowing into the extractor 706 throughlines 735 a–c and a fourth valve 752 d controlling the amount ofextraction fluid 736 supplied, via line 735 d, to a venturi valvedescribed below. Looking at FIG. 7B, the system 738 includes only asingle valve 752 for controlling the amount of extracting fluid flowinginto the extractor 706 through lines 735 a–cand into the venturi valvevia line 735 d. In both FIGS. 7A&B, the supply system 738 also includesa recycle line 754.

As the material-to-be-extracted 703 is being feed and mixed with theextraction fluid 736, any water and materials dissolved in the watermigrate across the membrane 710 into the lower section 712 a and exitthe extractor 706 via a line 713 to an aqueous phase storage tank 756via a control valve 758 a and a heat exchanger 758 b, where the controlvalve 758 a reduces the pressure to ambient pressure.

After the material-to-be-extracted 703 has been mixed with the threeportions of extraction fluid 736 in the extractor 706, the combinedmixture exits the extractor 706 via exit line 760 which interconnectsthe extractor 706 with a first separator 762. The separator 762 allowsthe solids to sink to a bottom section 764 a of the separator 762, whilethe fluids occupy a top section 764 b of the separator 762. Theseparator 762 also includes a venturi valve 766 connected to anextraction fluid input 768 connected to the supply line 735 d from theextraction supply system 738. As the extraction fluid 736 travelsthrough the venturi value 766, the solids 770 are pulled into theventuri valve 766 and exit the separator 762 to a solids recovery system772 via a solids outlet 771. The solids recovery system includes asolids storage vessel 772 a connected to the separator 762 via lines 772b having a pressure reducing control valve 772 c and a heat exchanger772 d. The separator 762 can also include a by-pass outlet 769 for theextraction fluid supplied to the venturi valve 766 via inlet 768.

The liquids, oils and extraction fluid, from the first separator 762 areforwarded to a second separator 774 through two pressure-reducingcontrol valves 776 a&b and two heat exchangers 778 a&b via lines 779.The second separator 774 includes hydrocarbon liquid exit line 780connected to a hydrocarbon storage vessel 781 via control valve 782. Thesecond separator 774 also includes probes 784, that determine the liquidlevel 785 in the separator 774, and an extraction fluid exit 786connected to the extraction fluid recycle line 754. Additionally, theextraction fluid by-pass outlet 769 from the venturi valve 766 isdirected via line 788 to a by-pass valve 789 and a regulator valve 790and combined with the liquids from the first separator 762 at the heatexchanger 778 a.

The preferred extraction fluid for use in the extraction system 700 ispure carbon dioxide, but the extraction fluid can be selected from thegroup consisting of Xe, NH₃, lower aromatic including benzene andtoluene, nitrous oxide, water, CO, CO₂, H₂O, lower alcohols includingmethanol, ethanol, propanol, and isopropanol, lower alkanes includingmethane, ethane, propane, butane, pentane and hexane, petroleum ether,lower alkenes including ethylene and propylene or mixtures orcombinations thereof, which may be formed, pressurized and preheated tojust below the critical temperature as described with reference to FIG.5.

The apparatus of the present invention can be located remote from thedrilling site or can be integrated into the drill complex. Thus, anoff-shore drilling platform could have an extraction unit built onto thepumping system for the drilling fluids so that the solids and aqueouscomponents could be separated on the hydrocarbon components which wouldinclude mud ingredients could be fed back into the downhole fluidstream.

Referring now to FIG. 8, a preferred configuration of a continuoussupercritical extraction system generally 800 of this invention forcleaning and/or desulfurizing liquids with only minor amount of solidstherein, such as used motor oils or fuels, is shown to include amaterial-to-be-treated supply system 802. The material-to-be-treatedsupply system 802 includes a material-to-be-treated reservoir 804containing the material-to-be-treated 806, a pump 808 or any otherapparatus for transferring a liquid material and a feed line 810.

The system 800 also includes an extracting fluid supply system 812. Theextraction fluid supply system 812 includes an extracting fluidreservoir 814 containing an extraction fluid 815, a compressor 816, anextraction fluid feed line 818 and a recycle line 820.

The system 800 is a multi-staged extraction/cleaning system shown inFIG. 8 to have four extractors 822 a–d in series and a separator 824.Each extractor 822 includes a membrane 826 separating each extractor 822into an upper section 828 and a lower section 830. The membranes 826allow water and polar compounds to migrated from the upper section 828of each extractor into the lower section of each extractor. The firstextractor 822 a is connected to the material-to-be-treated feed line810, while the other three extractors 822 b–d include a forwarding line832, which feeds the extractors 822 b–d with the contents of the uppersection 828 of the preceding extractor 822 a–c, i.e., the contents ofthe upper section 828 of the extractor 822 a is the feed for theextractor 822 b via forwarding line 832 and so on. Finally, the contentsof the upper section 828 of the extractor 822 d are forwarded to theseparator 824 via a separator feed line 834. Each extractor 822 alsoincludes an extractor feed line 836 connected to the feed line 818.Looking at FIG. 8B, each feed line 836 includes a separate flowcontrolling valve 838, where the valves 838 allow the amount ofextraction fluid 815 entering each extractor 822 a–d to be separatelycontrolled so that the amount of extraction fluid 815 being supplied toeach extractor 822 a–d can be different. Each extractor 822 a–d alsoincludes an aqueous phase outlet 840 connected to a waste aqueousstorage system 842 via waste lines 844. The storage system 842 includesa pressure reduction valve 846 and a heat exchanger 848 to reduce thepressure to ambient pressure and allow the temperature to warm to roomtemperature and a waste water storage container 850. The waste water canbe forwarded to a water treatment facility for further processing.

The separator 824 includes a finished product outlet 852 and anextraction fluid outlet 854. The finished product outlet 852 isconnected to a finished product storage system 856 via finished productline 858. The finished product storage system 856 includes a pressurereduction valve 860 and a heat exchanger 862 to reduce the pressure toambient pressure and allow the temperature to warm to room temperatureand a finished product storage container 864. The extraction fluidoutlet 854 is connected to the recycle line 820 passing through apressure reduction valve 866 and a heat exchanger 868 to reduce thepressure to ambient pressure and allow the temperature to warm to roomtemperature prior to mixing with the fresh extraction fluid going intothe compressor 816.

Although any extraction fluid described in this invention can be used inthe systems of FIGS. 7A&B and 8A&B, the system preferably uses purecarbon dioxide.

Additionally, if carbon dioxide is used in the extraction solventcomposition, then any of the previously described installation can beequipped with a low temperature separator for separating carbon dioxideout of the atmosphere. Additionally, the apparatus can have recyclingequipped to recover the extraction solvent for recycling.

Experimental Results

The supercritical extraction solvent used in the following examples wasstandard commercial grade Carbon Dioxide, from a stock cylinder. Thetype of cell used in the following examples was an 8 mL stainless steelview cell. The pump type used in the following examples was a Milton Roy100 ml/hour max, positive displacement pump. The samples used in thefollowing examples was a sample as received from Baker Hughes and wascentrifuged cuttings from well fluids. In all of the examples thefollow, the oil removal % was estimated or derived by sight only.

EXAMPLE 1

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 3,500 psi.

The supercritical extraction cell and pipework were cleaned withacetone. 1 g of the sample was placed in the cell and the cell wasreassembled. The cell was then placed into supercritrical pipe circuit.The cell and pipework were flushed twice with stock Carbon Dioxide. Thepressure was then increased to about 3,500 psi at ambient temperature.No color change in liquid phase was noted. The pressure was held atabout 3,500 psi pressure for about 1 hour and 20 minutes. The total oilremoved from the sample was about 99%. The solid material had a slighthydrocarbon sent, but dry to the touch.

EXAMPLE 2

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 1,000 psi and at 25° C.

The cell was cleaned and prepared as described in Example 1. Afterpreparation, the pressure was increased to about 1000 psi at atemperature of about 25° C. The pressure and temperature were maintainedfor about 1 hour. Under these conditions only partial oil removal wasachieved with the recovery being about 60%.

EXAMPLE 3

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 2,000 psi and at 27.8° C.

The cell was cleaned and prepared as described in Example 1. Afterpreparation, the pressure was increased to about 2000 psi at atemperature of about 27.8° C. The pressure and temperature weremaintained for about 20 minutes. Under these conditions only partial oilremoval was achieved with the recovery being about 85%.

EXAMPLE 4

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 2,500 psi and at 22.5° C.

The cell was cleaned and prepared as described in Example 1. Afterpreparation, the pressure was increased to about 2500 psi at atemperature of about 22.5° C. The pressure and temperature weremaintained for about 10 minutes. Under these conditions only partial oilremoval was achieved with the recovery being about 95%.

EXAMPLE 5

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 3,500 psi and at 43° C.

The cell was cleaned and prepared as described in Example 1. Afterpreparation, the pressure was increased to about 3500 psi at atemperature of about 43° C. The pressure and temperature were maintainedfor about 5 minutes. Under these conditions only partial oil removal wasachieved with the recovery being about 95%.

EXAMPLE 6

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 2,500 psi and at 43° C.

The cell was cleaned and prepared as described in Example 1. Afterpreparation, the pressure was increased to about 2500 psi at atemperature of about 43° C. The pressure and temperature were maintainedfor about 5 minutes. Under these conditions only partial oil removal wasachieved with the recovery being about 95%.

EXAMPLE 7

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 2,500 psi and at 23° C.

The cell was cleaned and prepared as described in Example 1. Afterpreparation, the pressure was increased to about 2500 psi at atemperature of about 23° C. The pressure and temperature were maintainedfor about 5 minutes. Under these conditions only partial oil removal wasachieved with the recovery being about 97%.

EXAMPLE 8

This example illustrates the cleanup of a sample of oil laden solidsobtained after well fluids are subjected to centrifugation undersupercritical conditions using CO₂ at 2,500 psi and at 23° C.

The cell was cleaned and prepared as described in Example 1. Afterpreparation, the pressure was increased to about 2500 psi at atemperature of about 23° C. The pressure and temperature were maintainedfor about 2 minutes. Under these conditions only partial oil removal wasachieved with the recovery being about 80%.

EXAMPLE 9

This example illustrates an analysis of a used oil after supercriticalcleanup using the apparatus of this invention and CO₂ as the extractingfluid.

The following table lists the properties of the treated oil:

Test Common Name Test Units Results ASTM D 482-95 Viscosity Index wt %0.365 ASTM D 93 Flash Point by PMCC ° F. 230+ ASTM D 1296-99 API Gravity@ 60° F. ° API 28.8 ASTM D 4077 Water Content vol % 6.32  ASTM D 445Kinematic Viscosity @ 100° F. cSt 24.470 ASTM D 4294-98 Total Sulfur wt% 0.327

EXAMPLE 10

This example illustrates the comparison of used oil before and aftersupercritical cleanup using the apparatus of this invention and CO₂ asthe extracting fluid.

The following table lists the properties of the oil before treatment:

Test Common Name Test Units Results ASTM D 482-95 Ash Content wt % 0.365ASTM D 93 Flash Point by PMCC ° F. 230+ ASTM D 1296-99 API Gravity @ 60°F. ° API 28.8 ASTM D 4077 Water Content vol % 6.32  ASTM D 445 KinematicViscosity @ 100° F. cSt 24.470 ASTM D 4294-98 Total Sulfur wt % 0.327

The following table lists the properties of the oil after treatment:

Test Common Name Test Units Results ASTM D 482-95 Ash Content wt % 0.005ASTM D 93 Flash Point by PMCC ° F. 190 ASTM D 1298 API Gravity @ 60° F.° API 33.9 ASTM D 4052 API Gravity @ 60° F. ° API 33.9 ASTM D 4077 WaterContent vol % 0.08 ASTM D 445 Kinematic Viscosity @ 100° C. cSt 2.904ASTM D 445 Kinematic Viscosity @ 100° F. cSt 11.62 ASTM D 445 KinematicViscosity @ 40° F. 10.71 ASTM D Distillation, 99% Recovery ° F. 9242887-97a - Ext'd ASTM D 1500-98 Color ASTM L2.0 ASTM D 2270-93 ViscosityIndex 124 ASTM D 4530-93 Carbon Residue (micro method) <0.1 ASTM D4294-98 Total Sulfur wt % 0.244 ASTM 6762 Nitrogen mg/Kg 46.0 AAS byAcid Iron ppm-wt 0.4 Digestion AAS by Acid Nickel ppm-wt <0.1 DigestionAAS by Acid Copper ppm-wt 0.2 Digestion

EXAMPLE 11

This example illustrates the comparison of used oil before and aftersupercritical cleanup using the apparatus of this invention and CO₂ asthe extracting fluid.

The following table lists the properties of the oil after treatment:

Test Value Test Value Viscosity Index. D-2270 85 Viscosity CST @ 40° F.,D-445 31.38 Appearance Clear & Bright Pour Point, ° F., D-97 <−10 yellowliquid Odor Petroleum Sulfur wt %, D-4294 0.2802 Viscosity SUS @ 210°F., D  43.0 Ash wt %, D-482 <0.001 Viscosity SUS @ 100° F., D-445 154.1Color, D-1500 1.5 Gravity API @  31.8 Actual flash point, COC D-92 400°F. Flash point, S.W. 101, ° F. 230+ Metals 0.10

EXAMPLE 12

This example illustrates the comparison of used oil before and aftersupercritical cleanup using the apparatus of this invention and CO₂ asthe extracting fluid.

The following table lists the properties of the oil before and aftertreatment:

Spec Before After Diff % Diff +/− Ash 0.365 0.005 0.360 98.6 DecreaseWater 6.32 0.03 6.29 99.5 Decrease Viscosity 24.47 2.904 21.566 88.1Decrease Flash 190 230 40 21 Increase API Gravity 28.8 33.9 5.1 17.7Increase Sulfur 0.337 0.244 0.093 27.7 Decrease

EXAMPLE 13

This example illustrates the comparison of used oil before and aftersupercritical cleanup using the apparatus of this invention and CO₂ asthe extracting fluid.

The following table lists the properties of the oil before and aftertreatment:

Spec Before After Diff % Diff +/− Ash 0.4  0.02 0.38 95 Decrease Water6.4 0.4 6.0 93.75 Decrease Flash 200+   200+   — — — Sulfur 0.3 0.3 — ——

EXAMPLE 14

This example illustrates the comparison of used oil before and aftersupercritical cleanup using the apparatus of this invention and CO₂ asthe extracting fluid.

The following table lists the properties of the oil before and aftertreatment:

Parameter Test Method Detection Limit Before After Gravity API @ 60° F.D-287 — 28.2 29.7 Flash Point, ° F. S.W. 1010 −10 BFO 380 Viscosity CST@ 40° C. D-445 1 24.37 35.63 Pour Point, ° F. D-97 −10 <−10 <−10 Sulfur,wt % D-4294 0.0001 0.3116 0.3019 Ash, wt % D-482 0.001 0.315 0.004 TotalHalogen, PPM D-808 1.0 617.2 10.6 PCB's, PPM S.W. 8082 0.05 BDL BDLWater by distillation, Vol % D-95 0.05 6.4 <0.05 Sediment by Extraction,wt % D-473 0.01 0.05 <0.01 Heat of Combustion, BTU/lb D-240 10 17,76119,302 Heat of Combustion, BTU/gal D-240 60 131,040 141,078 CarbonResidue Ramsbottom, wt % D-524 0.01 — 0.06 Heavy Metals PPM MethodDetection Limit Before After Arsenic EPA-6010 0.0012 BDL BDL CadmiumEPA-6010 0.0015 0.113 0.014 Chromium EPA-6010 0.0040 0.525 0.007 LeadEPA-6010 0.0140 9.693 0.338 Nickel EPA-6010 0.0055 4.021 BDL SodiumEPA-6010 0.0010 66.277 1.823 Vanadium EPA-6010 0.0020 0.030 0.015 IronEPA-6010 0.0015 31.981 0.351 BDL—beyond detection limit; BFO—Blows flameout @ 200° F. Recovery, D-86 Distillation, ° F. Recovery, D-86Distillation, ° F. IBP 542 70% Recovery 728  5% Recovery 602 80%Recovery 740 10% Recovery 670 90% Recovery 756 20% Recovery 690 95%Recovery 788 30% Recovery 700 End Point 796 40% Recovery 708 Recovery98.0% 50% Recovery 714 Residue 1.5% 60% Recovery 718 Loss 0.5%

EXAMPLE 15

This example illustrates the analytical data for the oil extracted froma drilling fluid under supercritical cleanup using the apparatus of thisinvention and CO₂ as the extracting fluid.

The following table lists the properties of the drilling fluid recoveredoil:

Test Parameter Method Results Gravity API @ 60° F. D-287 38.0 FlashPoint, PMCC ° F. D-93 148 Viscosity CST @ 100° F. D-445 2.73 Pour Point,° F. D-97 -5 Cloud Point, ° F. D-2500 10 Sulfur, wt % D-4294 0.0615 Ash,wt % D-482 <0.001 Color D-15 0.5 PCB's, PPM S.W. 8082 BDL Water bydistillation, Vol % D-95 <0.05 Sediment by Extraction, wt % D-473 <0.01Carbon Residue Ramsbottom, wt % D-524 0.06 Carbon Residue Ramsbottom, wt% D-524 0.20 on 10% residue Cetane Index D-976 54.0 Bacteria Count,Counts/mL — 0 Heavy Metals PPM Method Before Arsenic EPA-6010 BDLCadmium EPA-6010 BDL Chromium EPA-6010 0.006 Lead EPA-6010 0.254 NickelEPA-6010 BDL Sodium EPA-6010 0.572 vanadium EPA-6010 BDL Iron EPA-60100.039 BDL—beyond detection limit; BFO—Blows flame out @ 200° F.; samedetection limits as in Example 14 Recovery, Recovery, D-86 Distillation,° F. D-86 Distillation, ° F. IBP 354 70% Recovery 578  5% Recovery 39680% Recovery 600 10% Recovery 408 90% Recovery 636 20% Recovery 438 95%Recovery 674 30% Recovery 460 End Point 698 40% Recovery 482 50%Recovery 528 60% Recovery 554 Accelerated Stability, F 21-61 ValueInitial Color 0.5 Final Color 1.0 Pad Rating (Blotter) 1  

All references cited herein are incorporated by reference. While thisinvention has been described fully and completely, it should beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. Although theinvention has been disclosed with reference to its preferredembodiments, from reading this description those of skill in the art mayappreciate changes and modification that may be made which do not departfrom the scope and spirit of the invention as described above andclaimed hereafter.

1. A process for cleaning a material comprising the step of: charging aquantity of a material-to-be-treated selected from the group consistingof drilling fluids, reactor sludges, oil-contaminated soils, oilcontaminated water, used oil, hydrocarbon fuels, tar sands, tankerbottoms, refinery bottoms, oil pit residues, refinery waste streams,refinery residue streams, paint wastes, and polymer wastes, where thematerial-to-be-treated comprises water and water soluble aqueouscomponents, a non-aqueous fluid, and solid materials into an interior ofan inner tube of a tubular extraction vessel comprising: an upperportion including an outer tube, an middle tube, and the inner tube; asemi-permeable membrane; and a lower portion, charging a quantity of CO₂to a plurality of interior sites of the tubular reactor until the fluidis at or above its critical point, contacting the material-to-be-treatedwith the CO₂ under conditions of temperature and pressure sufficient tomaintain the fluid at, near or above its critical point to produce atreated material comprising the CO₂, the non-aqueous fluid and the solidmaterials; concurrently, removing water and water soluble components viathe semi-permeable membrane into the lower portion of the tubularextraction vessel to produce an aqueous product, forwarding the treatedmaterial into a first separation vessel comprising an interior, atreated material inlet, a fluid outlet and a solids outlet having aventuri valve, removing the solid materials from the first separationvessel through the venturi valve to a solids storage container toproduce a solids product, removing a fluid comprising the non-aqueousfluid and the CO₂ from the first separation vessel and forwarding thefluid to a second separation vessel having a fluid level sensor,separating the fluid in the second separation vessel into used CO₂ and anon-aqueous fluid product, and transferring the non-aqueous fluidproduct to a fluid storage container.
 2. The process of claim 1, whereinthe material-to-be-treated is a drilling fluid and the non-aqueous fluidproduct comprises a hydrocarbon product substantially free ofcontaminants, and the solids product is substantially free ofhydrocarbons and other contaminants.
 3. The process of claim 1, whereinthe material-to-be-treated is a used oil and the non-aqueous fluidproduct comprises a cleaned oil substantially free of water and watersoluble contaminants and substantially free of solids.
 4. The process ofclaim 3, wherein the cleaned oil has a lower sulfur content than theused oil prior to cleaning.
 5. The process of claim 1, wherein thematerial-to-be-treated is a hydrocarbon fuel and the non-aqueous fluidproduct comprises a cleaned fuel having a lower sulfur content than thehydrocarbon fuel prior to cleaning.
 6. The process of claim 1, whereinthe material is a hydrocarbon contaminated soil and the non-aqueousfluid product comprises a hydrocarbon product substantially free ofsolids, water and water soluble contaminants, the solids productcomprises a cleaned soil substantially free of hydrocarbon and othercontaminants, and the aqueous product is substantially free ofhydrocarbon.